This invention relates to hydraulic brake pressure control valves adapted for use in vehicle braking systems.
Various types of hydraulic brake pressure control valves have been proposed and utilized for controlling the brake pressure in rear wheel brakes as compared with that in front wheel brakes such that the brake pressure in the rear wheel brakes is limited to a predetermined pressure or that the brake pressure in the rear wheel brakes is reduced as compared with the front wheel brakes in the higher ranges of applied brake pressure. Such valves can effectively avoid premature rear wheel skidding.
However, in vehicles such as trucks or the like, the skidding condition in the rear wheel brakes varies substantially between the light-loaded condition and the heavy loaded condition, and a hydraulic brake pressure control valve adjusted for the light-loaded condition cannot supply the pressure required to effectively stop the vehicle in the heavy-loaded condition. Thus, there have been proposed load-responsive type hydraulic pressure control valves. However, there are shortcomings in such valves, for example that the construction is complicated, and the adjustment during installation of the valves is difficult since some of them have external links or the like connecting the valves with load detecting means or the like.